On the driving techniques for high-brightness LEDs

High-brightness light-emitting diodes (HBLEDs) are conventionally driven in the amplitude mode (AM) or pulse-width-modulation (PWM) mode. High luminous efficacy is obtained with AM, but precise dimming is difficult to achieve and such AM-driven LEDs suffer from significant color variations. PWM offers excellent dimming capability and color stability but the LEDs acquire lower luminous efficacies compared to AM. The advantageous features of both conventional methods can be united in a single generalized methodology as proposed in this paper. It utilizes pulsating current while enables simultaneous adjustments of the current levels and duty cycle for achieving a predetermined luminous efficacy and dimming range of interest to the users. The dimming dynamics using the proposed method is investigated through a detailed parametric study by experiments and numerical calculations.